added OK|FAIL for ULKDUP
Fixed some protocol details (persistence-broker)
Changed protocol spec to RFC2119 syntax and extended it slightly.
Second protocol added.
"OK" code is better for parsing.
persistence proto: Various changes

* Disallow usage of spaces as field delimiters
* Use more consistent environment variables
For INET sockets, specify port in separate env var.
Some protocol changes at the webapp-mesgbroker protocol.
Architecture diagram update
Protocol draft message_broker←→message_relay
Preliminary implementation of persistence layer

Limitations:
* no error checking whatsoever
* does only support unix domain sockets
* only the auth commands (UREG, CHKPASS) are implemented
Also support INET/INET6 sockets